Powerline pulse position modulated transmitter apparatus and method

ABSTRACT

A transmitting controller is connected to a powerline and on command places a reference signal and a series of signal pulses in the powerline at a series of signal timing positions related to zero voltage crossing points so that the signals pulses are substantially in the powerline temporal quiet zone near zero crossing. The signal pulses are produced from a pair of capacitors and switches which are each sequentially charged a first polarity from the powerline and is discharged in the powerline at the opposite polarity so that the powerline voltage at the time of the pulse is additive to the pulse voltage. The receiving controller is connected to the powerline and has a filter circuit therein which filters away the powerline AC signal and noise to leave the reference and signal pulses. The signal pulses are compared to the position of starting reference pulses to determine in which signal timing position the pulses have occurred. Digital data is communicated over the powerline in accordance with the position placement of the data pulses related to the reference pulse positions. The timing quiet zone for transmission and signals is preferably about 500 to about 1000 microseconds away from zero voltage crossing.

CROSS-REFERENCE

This invention is related to my prior applications, entitled “ZEROCROSSING BASED POWERLINE PULSE POSITION MODULATED COMMUNICATION SYSTEM”,application Ser. No. 09/656,160, filed Sep. 6, 2000, now patent No.6,734,784, granted May 11, 2004; and “SYNCHRONIZATION REFERENCE PULSEBASED POWERLINE PULSE POSITION MODULATED COMMUNICATION SYSTEM,” filedJun. 6, 2001, application Ser. No. 09/879,874, now patent No. 6,784,790,granted Aug. 31, 2004. This application relies for priority upon myprior Provisional Application entitled “POWERLINE PULSE POSITIONMODULATED TRANSMITTER APPARATUS AND METHOD,” filed Apr. 22, 2004.

FIELD OF THE INVENTION

This invention is directed to an apparatus which enables thetransmission of digital communication between two or more deviceswherein the devices are connected to the same powerline and use the samepowerline to receive power and as a physical channel for electronicintercommunication.

BACKGROUND OF THE INVENTION

There are devices which are more conveniently used if they can beremotely controlled. In a household, such devices are mostly appliancesand lighting loads. The appliances and lighting loads may be remotelycontrolled for a number of different reasons. For example, for nightsecurity, some lights may be controlled by a timer.

In other cases, different lighting intensity and different lightingdistribution may be desirable in a single room, depending upon its use.The room may be used for reading, conversation or watching displays,such as television. Each suggest a different lighting level anddifferent lighting distribution. Normally, people do not make suchchanges because it is inconvenient to do so. Therefore, it is desirableto have a convenient, reliable way to remotely control lighting systems.

In addition to lighting systems, other devices can be convenientlyremotely controlled. For example, powered gates and garage doors can beremotely controlled. An electric coffee pot may be turned on at anappropriate morning hour. Powered draperies may be opened and closed,depending upon sun altitude.

As electronic technology has advanced, inventors have produced a varietyof control systems capable of controlling lighting and other electricloads. In order to be useful as a whole-house lighting control system,there are certain requirements that must be met. A system must permitboth small and large groups of lights to be controlled on command. Theproblem is the connection between the controller and the lighting load.Such connection may be hard-wired, but such is complex and veryexpensive to retrofit into an existing home. Another connection systemmay operate at radio frequency, but this has proven difficult toimplement because the FCC requires low signal levels which are subjectto interference and because the transmission and receiving circuitry iscomplex and expensive.

It must be noted that both the controller and the load to be controlledare connected to the same powerline. It would be useful to use thepowerline as the communication-connecting channel. Prior powerlinecommunication schemes have had difficulties employing the powerline as acommunication channel because the communication signals after beingattenuated by the powerline circuitry are very small compared to thebackground noise. It is impossible to avoid the fact that betweencertain locations in a residence there will be very high attenuation ofany transmitted signals. It has been difficult to reliably separate thehighly attenuated communication signals from the background noise on thepowerline.

The situation is further aggravated and complicated by the fact that thenoise and attenuation parameters are constantly and unpredictablychanging as loads are connected and disconnected both inside the primaryresidence and inside any of the many neighboring residences attached tothe same mains power transformer. In reality the powerline circuit usedfor communication in a residence includes all the residences attached tothe mains power transformer. There is no practical way to avoid thecomplications caused by this fact.

SUMMARY OF THE INVENTION

In order to aid in the understanding of this invention, it can be statedin essentially summary form that it is directed a specializedtransmitter circuit and method to enable powerline pulse positionmodulated communication. The transmitting device senses the zero voltagecrossing point in the powerline and transmits a series of signal pulsesat a set of specified positions, the position of the data pulse relativeto either the zero crossing time or the position of the startingreference pulses representing digital data in the form of a digitalnumber. The set of all possible relative positions is in the quiet zoneadjacent, but spaced from the main voltage zero crossing point. Theenergy needed to produce the signal pulses are stored in the capacitor.When the pulses are released to become a data pulse, they are releasedin the opposite half cycle from which they are charged. Thus, theamplitude of the pulse with respect to the zero crossing is the voltageof the power wave at the time of the pulse with respect to zerocrossing, plus the voltage of the pulse with respect to zero crossing.The receiving circuit also senses the voltage zero crossing point andcan reliably detect the signal pulse in the background powerline noisebecause of the knowledge of where the signal pulse is expected in thequiet zone adjacent, but away from the zero crossing point and becauseof the high magnitude of the very robust signal pulse even aftersignificant residential attenuation. Since the data pulse is a voltagespike equal to the line voltage at the pulse point plus the discharge ofthe capacitor, the pulse can be more readily detected. After determiningin which one of the possible relative positions the signal pulse waslocated, the associated digital data in the form of a digital number iseasily determined. Thus digital data is communicated from one devicethrough the powerline to another device using this method of powerlinepulse position modulation. This patent describes a specificconfiguration of transmitting circuit and operation of that circuit toderive transmission signals that are much more effective that thepreviously described transmitter circuits. This transmitter circuit usestransmission components that are triggered in such a manner as toproduce communication pulses in the next half cycle after the charginghalf cycle so that at the time the transmission pulse is produced thepulse voltage is additive to the line voltage with respect to zero whichproduces the most robust pulse possible that is derived directly fromline voltage.

It is a purpose and advantage of this invention to provide a method andapparatus for reliable transmission of digital data over the powerlineby means of a powerline pulse position modulation communication methodutilizing a novel dual capacitor, dual switch circuit to provide muchmore robust data pulses when compared to our previous powerline pulseposition modulation communication method that have only one availablecapacitor and switch to produce the necessary series of pulses.

It is a further purpose and advantage of this invention to provide amethod and apparatus for powerline pulse transmission wherein thevoltage zero crossing is sensed and the communication signal pulse istransmitted and sensed in a receiver based on the signal positionrelative to either the zero crossing point or the position of one ormore of the previous transmitted pulses.

It is a further purpose and advantage of this invention to provide amethod and apparatus by a powerline pulse position modulationtransmission method for the purpose of remote electrical load control.

It is a further purpose and advantage of this invention to provide amethod and apparatus wherein the voltage zero crossing is sensed, anddigital pulse windows are defined with respect to the zero voltagecrossing, but spaced from the zero voltage crossing so as not tointerfere with other equipment using the zero voltage crossing time forvarious purposes.

It is a further purpose and advantage of this invention to provide amethod and apparatus by a powerline pulse position modulationcommunication method for the purpose of remotely retrieving operationaldata from residential appliances.

It is a further purpose and advantage of this invention to provide amethod and apparatus by a powerline pulse position modulationcommunication method for the purpose of remotely controlling residentialloads for utility company energy management.

It is another purpose and advantage of this invention to provide apowerline pulse position modulated communication apparatus and methodwhich complies with FCC regulations relating to apparatus which isconnected to and communicating on the powerline.

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The present invention,both as to its organization and manner of operation, together withfurther objects and advantages thereof, may be best understood byreference to the following description, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic electrical diagram of the powerline pulse positionmodulated communication apparatus in accordance with this invention.

FIG. 2 is a schematic electrical diagram of how a plurality of suchapparatus is used to control plural lighting loads in a room.

FIG. 3 is a schematic electrical diagram of how a plurality of suchapparatus is used to control the lighting load in a plurality of rooms.

FIGS. 4A, 4B, 4C and 4D show the powerline waveforms containing thecommunication signals therein as utilized by the previous methods and inmy previous applications.

FIGS. 5A, 5B, and 5C are powerline waveform diagrams showing thetransmission positions employed by the apparatus of this invention forthe half of the transmission circuit charging on the positive halfcycles and discharging on the negative half cycles.

FIGS. 6A, 6B, and 6C are powerline waveform diagrams showing thetransmission positions employed by the apparatus of this invention forthe half of the transmission circuit charging on the negative halfcycles and discharging on the positive half cycles.

FIG. 7A, 7B, 7C, 7D and 7E are powerline waveform diagrams showing thetransmission positions employed by the apparatus of this invention forcombination of both transmitter sections described in FIG. 5 and FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The purpose of the powerline pule position modulated communicationtransmitter apparatus of this invention as shown in FIG. 1 is to enablethe communication of digital data from one device to another by means ofthe powerline to which both devices are connected. A further purpose isto enable communication with appliances and to control lighting or otherelectrical loads in one or more rooms of a residence.

Application Example Lighting Control System

A lighting control system as shown in FIG. 2 and FIG. 3 will be used asan example of an application in this description of this invention.

In FIG. 2, transmitting controller 10 is supplied with conventionalhousehold electric power from circuit panel 12. Circuit panel 12 issupplied from commercial powerline and has two or three outputs. In thepresent example, the circuit panel 12 has a neutral line 14 andpowerlines 16 and 18. Further, the powerlines 16 and 18 inside adomestic residence are derived from a center tapped 240 vac transformerand are each nominally at 120 rms volts with respect to neutral line 14.The voltage waves in powerlines 16 and 18 are at a 180 degree phaseangle with respect to each other.

Also connected to the powerline 18 and neutral 14 are lighting loadreceiving controllers 20, 22 and 24. These receiving controllers arerespectively connected to loads 26, 28 and 30. The loads are electriclights, in this example, but may be heater or motor loads as describedabove. Furthermore, the receiving controllers 20, 22 and 24 are capableof receiving digital commands which change the supply of power to theloads and may supply different levels of power to the loads to controlthe brightness of the lighting load. The transmitting controller 10emits its digital commands into the powerline 18 for transmission to thereceiving controllers 20, 22 and 24 by pressing one or more of thecommand buttons 160, 34 and 36 on transmitting controller 10. Thus, thereceiving controllers 20, 22 and 24 receive digital commands from thetransmitting controller 10 to control the loads 26, 28 and 30,respectively. No separate wiring or radio frequency communication isrequired, but the transmitting controller places signals in thepowerline 18. Such transmitted signals are coded so that they can bedetected by all of the receiving controllers.

A similar arrangement is seen in FIG. 3 wherein a main circuit panel 12supplies power to four different rooms. The lighting and other loads inthe four different rooms can be separately controlled in each room orcan be controlled by a master, whole-house controller 44. Assuming roomNo. 1 in FIG. 3 is the same as the room in FIG. 2, it is seen that room2, room 3 and room 4 are identical. Each room has a transmittingcontroller the same as controller 10 and three receiving controllers,the same as controllers 20, 22 and 24. Each of the receiving controllerscontrols a load, the same as loads 26, 28 and 30, respectively. Each ofthe transmitting controllers 38, 40 and 42 is identical to thetransmitting controller 10, and each places digital command signals intothe powerline.

However, the receiving controllers are programmed to act only on therelevant command data. The response of the receivers is determined bythe preprogrammed address and command-interpreting program locatedwithin each receiver. Thus, the loads in four or more rooms may each becontrolled by a transmitting controller.

In addition, transmitting master controller 44 is connected to thepowerline. It is identical to the transmitting controllers 10, 38, 40and 42, but it is programmed differently to send out digital datasignals which command receiving controllers to control their loadsindividually. The fact that transmitting controller 44 is connected onlybetween powerline 18 and neutral 14 does not interfere with its abilityand function to send signals to receiving controllers connected betweenpowerline 16 and neutral 14.

Transmission and Receiving Circuit Operation

The transmitting controllers 10 and the receiving controllers 20 areidentical, in the sense that they contain the same transmitting andreceiving circuitry. They are programmed differently so as to achievethe desired different results. The controller 10 is schematicallyillustrated in FIG. 1. It has a transmitting circuit 46, which isconnected to powerline 16 through line 48 and to neutral through line49. The transmitting circuits comprises a pair of identical circuits,the first circuit consisting of triac 50 which is connected in serieswith energy storage capacitor 52. Inductor 54 is also in the seriesconnection between line 48 and capacitor 52. Capacitor 56 forms a lowpass filter with inductor 54 to minimize high frequency emissions sothat the transmitter meets the FCC requirements. Triac 50 is controlledby line 58 which is the output from digital control integrated circuit60. Hereinafter, the conventional abbreviation “IC” will be used inplace of the term “integrated circuit.” When the digital control ICsends an appropriate firing signal on line 58, the triac fires and putsa pulse in line 16 with respect to the neutral 14. The second identicalcircuit consists of a second triac 51, capacitor 53 and inductor 55. Thefilter capacitor 56 is common to both transmission circuits.

Controller 10 also contains a receiver circuit 62. The importantcomponents of the receiver circuit 62 form a band pass filter circuit.This includes capacitor 66, capacitor 68, capacitor 76, inductor 70,inductor 74 and inductor 64. Resistor 72 limits the current through thecircuit. Resistor 78 is connected in series to limit the current insignal line 80. This circuit filters the signal pulse out of thepowerline 60 cycle voltage and background noise.

Signal line 80 is connected into digital control IC 60 as its signalinput. As a particular example, digital control IC 60 is amicroprocessor Microchip model PIC16F87. The input signal line 80 isconnected between two clipping diodes 82 and 84 to protect the digitalcontrol IC 60 from excessively high and low voltages. The signal inputline 80 is connected to comparator 86 where the signal voltage iscompared to internal voltage reference 88. The voltage reference 88,which is adjustable by the digital control IC 60 allows the digitalcontrol IC 60 to automatically adjust the receiving signal level to beset above the noise level. This is a form of automatic gain controlwhich is essential so that the digital control IC 60 can discriminatebetween noise and real signal pulses. The comparator output 90 carriesthe received digital signal to the internal processing circuitry of thedigital control IC.

There are additional inputs to the digital control IC 60. Zero crossingdetector 92 is connected to powerline 16 and neutral 14. It has anoutput to the digital control IC 60. Power supply 94 supplies power tothe digital control IC and to the EEPROM memory 96. There may be aplurality of the input switches, one of which is indicated at 98, forcausing the digital control IC 60 to perform some internal operation orto issue transmitted commands. The commands of switch 98 correspond tothe command buttons 160, 34 and 36 seen in FIG. 2. It is desirable thatthere be some method of visual feedback to the user for a variety ofprogramming and control uses. This is provided by indicator light 100,which may be energized by the digital control IC 60. When the controller10 is acting as a receiver load controller, it has an output circuitwhich controls the load. This output device 102 is in the form of arelay, triac, or the like. It controls the flow of power from line 16 tothe load 104.

Pulse Position Modulation of Digital Data

FIG. 7E shows a sine wave 104 which represents the powerline voltage inone of the lines 16 or 18 of FIG. 2, as compared to neutral. Eight halfcycles are shown. For the purpose of this disclosure, the powerlinefrequency is 60 cycles per second, which is the modern domesticstandard. The voltage shown is nominally 120 volts rms, with peaks atabout 160 volts, plus and minus. These are examples, and the apparatusand method can be utilized with other voltages and frequencies. Taking60 cycles per second as the preferred embodiment, each half cycle, whichis each of the intervals T, in all figures, is 8.333 milliseconds.

Transmitter Operation

In FIG. 7E, the voltage through the time periods T1, T2, and T3 is aplain sine wave 104 with no communication pulses. During the next fivehalf cycles, T3 through T8, there is a superimposed pulse on the sinewave near to each of the positive and negative zero crossing points. Onepositive and one negative zero crossing point are indicated at 105 and107 respectively. In FIGS. 7A, 7B, 7C and 7D, the zero crossing point isrepresented as the transition from one time period to the next. Thesesuperimposed pulses are the means of communication. The transmittingdevice places these pulses on the powerline. Receiving devices detectthese pulses on the powerline.

Each pulse can represent one transmitted data number. The numbertransmitted can range from 1 to N where N is the total number ofpossible positions of one pulse. In FIGS. 5C and 6C a sine wave is shownwith the four positions highlighted in each half cycle. Positions number0,1,2, and 3 are identified on FIG. 5, half wave T3 as 180, 182, 184,and 186, respectively and in FIGS. 5C and 6C, half wave T4 as 170, 172,174, and 176, respectively. The current embodiment utilizes fourpositions located in the quiet zone spaced from, but just before zerocrossing.

If the total time allotted to the four positions is 400 uS then thespacing of each position relative to the next possible position will be100 uS. This is shown in FIGS. 5C and 6C. By placing a pulse in one ofthe possible four positions, one numeric digit, from 0 to 3, can betransmitted every half cycle. In binary, this is equal to two bits perhalf cycle. Up to 256 positions are possible with current microprocessortechnology. In binary, a number with 256 possible states is equal toeight bits or one byte per half cycle.

When a powerline transmission consisting of a series of pulses isdesired, the first need is to charge the capacitor 52 in FIG. 1. Beforethe initial charging the initial charge state of the capacitor 52 isunknown. The digital control IC puts an initial trigger pulse 170, seeFIG. 5A, in line 58 to begin turning on triac 50 to begin chargingcapacitor 52. The initiating pulse is preferably near a zero crossingbut is not critical. This turns on the triac 50, and the capacitor 52begins charging. FIG. 5B shows the voltage across capacitor 52, and thestart of its charging is shown at point 105. The curve in FIG. 5B afterthe point 105 is the traditional capacitor charging curve. This does notyet produce a pulse in the powerline. Once the triac 50 is conductive,another initiating trigger pulse for charging is not necessary. Once thetriac is charged and discharged, it will continue to charge in theopposite polarity and will be ready to discharge in the next half cycle,as seen in FIG. 5B. The triac turns off and the capacitor stops chargingeach time the charging current through the triac 50 reaches zero, whichoccurs at every peak of the mains sine wave, which is shown at 104 inFIG. 5B. When it is desired that a signal pulse be placed on thepowerline, digital control IC 60 places a trigger pulse in line 58 tofire triac 50. These trigger pulses are shown at 172, FIG. 5A. Thispulse produces conduction in triac 50 to create the corresponding signalpulse 178, in the powerline, as shown in FIG. 5C. The waveform in FIG.5B is shown as a reference of the voltage across transmitting capacitor52 as it is charged and discharged. As it is discharged every other halfcycle, which is shown in FIG. 5C in the negative half cycles, a pulse isproduced in the powerline.

The fact that the capacitor charge voltage is so much greater if thecapacitor is discharged in the following half cycle as opposed to thesame half cycle in which the charging began is the fundamental reasonthe pulse strength in this method is so strong. In the half cyclefollowing charging, the powerline voltage is opposite that of thecapacitor voltage and thus the two are additive to produce a strongpulse signal.

In order to be compatible with the transmission circuits and methods ofprior it is necessary to produce messages consisting of one pulse perhalf cycle. With the present method discussed above and shown in FIGS.5, 6 and 7 using only one capacitor in series with one switch, only onepulse can be produced on every other half cycle. Therefore twoindependent capacitor/switch circuits are required to combine theirresulting pulse trains occurring on every other half cycle into onecomposite pulse train with one pulse on every half cycle. This compositepulse train with the two pulse trains of FIG. 5 and FIG. 6 combined isshown in FIG. 7.

The simple reason this method of producing transmission pulses issuperior to the method using a single capacitor is shown clearly inFIGS. 4B and 5B. In FIG. 4B the voltage across the capacitor at the timeof discharge is approximately 120 V. In FIG. 5B the voltage across thecapacitor at the time of discharge is approximately 240 V. The largervoltage difference in FIG. 5B at the time of discharge produces a muchstronger pulse. The larger pulse in turn produces more reliabletransmission and communication. It has been found that this strongermethod of transmitting works in certain high attenuation applicationswhere the single capacitor method is unreliable. The seemingly obviousmethod of increasing signal strength by increasing the size of thetransmitting capacitor does not work. Increasing the size after acertain size produces no change in the signal strength. The novel methodutilized by this invention produces a very large increase in signalstrength.

The reason two separate capacitor, switch transmission circuits areneeded is because that the time between charging and discharging of onecapacitor is more than one half cycle therefore each capacitor can onlyproduce one pulse on every other half cycle.

Since only one pulse can be transmitted per half cycle with this circuitdesign, one and only one number can be transmitted each half cycle. Thereason this method of modulating data is named “pulse positionmodulation” herein is because the value of the data is encoded in theposition of the pulse.

Because of attenuation, background noise, and other periodic andintermittent random noise pulses present on the powerline, these signalpulses would ordinarily be difficult to detect. However, in accordancewith this invention, when the pulse is stronger or of greater magnitudeit is easier to detect.

To summarize, there are four primary reasons the area from 1000 uS to500 uS before zero crossing is selected for our transmission period.First, because a relatively large pulse is generated because thecapacitor is charged to a large voltage. Second, because there is arelatively is charged to a large uniform voltage from the beginning ofthis period to the end of this period. Third, because there is littleinterference caused by the communication pulses to devices that utilizethe powerline zero crossing for various purposes, such as clocks orlight dimmers. Fourth, because there is very little noise from pulseproducing devices, such as light dimmers, during this period. The noveldesign presented here is for a simple method of greatly increasingsignal strength of each transmitted pulse to increase overallcommunication reliability.

The manner of operation of this receiving circuit 62 in FIG. 1 has beendiscussed above. It is connected to the line and awaits the incomingpulse. The powerline frequency and noise are filtered out, but thesignal pulse can readily be detected because it is within the 1000microsecond quiet zone near the zero crossing point. When the pulse issensed, the signal position in which it is located is determined by theDigital Control IC 60.

In a message transmission on each half cycle one pulse is received. Apulse may be a reference pulse at the start of the message or a datapulse following one or more reference pulses. Each pulse will be in oneof several possible temporal positions that may be referenced to zerocrossing or a previous reference or data pulse. Each of the possibletemporal positions will represent a different data number. If there arefour positions, as in the current embodiment, then one of the numbers,0,1,2 or 3 can be transmitted by one pulse in one half cycle. A stringof these pulses and derived numbers are combined to make a completemessage.

This is the fundamental method of transmitting and receiving numericaldata. This series of numerical data is stored in the Digital control ICand processed according to the application program requirements. If thedevice is a lighting controller, the data would most likely representlighting system addresses and command instructions. Other applicationswould have other meanings for the decoded data. Some application devicessuch as a powerline modem might use the invention for pure communicationof data and may not have a specific application function.

This invention has been described in its presently contemplated bestembodiment, and it is clear that it is susceptible to numerousmodifications, modes and embodiments within the ability of those skilledin the art and without the exercise of the inventive faculty.Accordingly, the scope of this invention is defined by the scope of thefollowing claims.

1-41. (canceled)
 42. A powerline pulse position modulated systemcommunication method for remotely controlling a load, comprising thesteps of: providing a transmitting controller with a connection to thepowerline; said transmitting controller incorporating a transmissioncircuit including a switch in series with a capacitor in series with anoptional inductor, said switch, capacitor and inductor connected orcoupled to line and neutral of the powerline in a single or three phasesystem or to a first and a second phase line in a three phase system;sensing zero voltage crossing time in the powerline; sensing a loadcontrol command causing the creation of a powerline control messageconsisting of one or more data pulses placed in predetermined signaltiming positions related to the zero voltage crossing time; each of saidpulses generated by the discharging of a said capacitor by said switchin a half cycle of the powerline that is opposite in polarity andfollowing a half cycle in which said capacitor finished charging;providing a receiving controller with a connection to the powerline;sensing by said receiving controller the zero voltage crossing time inthe powerline; sensing by said receiving controller the one or more datapulses; and actuating the load depending upon in which of saidpredetermined signal timing positions the data pulses occurred.
 43. Themethod of claim 42 wherein said transmitting controller employs arectifying device connected in parallel with said switch to providecharging of said capacitor.